一个前向安全无证书代理签名方案的安全性分析*

对一个前向安全无证书代理签名方案进行分析，指出这个方案既不具有不可伪造性，也不具有前向安全性。证明了该方案对于公钥替换攻击是不安全的，即敌手通过替换原始签名者和代理签名者的公钥可以伪造该代理签名者对任意消息的代理签名，给出了伪造攻击方法。指出该方案不具备前向安全性的原因，即该签名方案的代理密钥更新算法没有利用时段标识，代理签名没有明确包含时段信息。

Security analysis of forward secure certificateless proxy signature scheme

A forward secure certificateless proxy signature scheme was analyzed, and it was pointed out that the scheme is neither unforgeable nor forward secure. It was showed that the scheme is insecure under the public key replacement attack. The adversary can forge a proxy signature for any message of any proxy signer by substituting the public keys of the original signer and the proxy signer. The attack method is given in detail. The reason without the forward secure property is that the updating algorithm of proxy private keys of the scheme does not use time periods and the proxy signatures do not explicitly include period identities. So the scheme is not a forward secure signature scheme.